(a) Field
The invention relates to a bacterial inoculant composition to improve production of sucrose-rich crops with reduced use of nitrogen fertilizer.
(b) Description of Prior Art
Nitrogen is an essential plant nutrient for plant growth, being an indispensable building block of amino and nucleic acids.
Nitrogen-based fertilizers, which are inorganic fertilizers, are most commonly used to treat fields used for growing maize, followed by barley, sorghum, rapeseed, soybean and sunflower. Nitrogen fertilizer is often synthesized using the Haber-Bosh process, which produces ammonia. This ammonia is then used to produce other compounds, notably anhydrous ammonium nitrate and urea, which can be applied to fields.
High application rates of inorganic nitrogen fertilizers in order to maximize crop yields, combined with the high solubility of these fertilizers, lead to increased leaching of nitrates into groundwater (C. J. Rosen and B. P. Horgan, Preventing Pollution Problems from lawn and garden fertilizers, 2009, University of Minessota Extention). Eventually, nitrate-enriched groundwater will make its way into lakes, bays and oceans where it accelerates the growth of algae, disrupts the normal functioning of water ecosystems, and kill fish in a process called euthrophication. The use of ammonium nitrate in inorganic fertilizers is particularly damaging, as plants absorb ammonium ions preferably to nitrate ions. This allows excess nitrate ions which are not absorbed to be freely dissolved (by rain or irrigation) into groundwater and other waterways, leading to euthrophication.
Application of nitrogen fertilizer to plants to increase their productivity can have negative and unpredictable effects on the environment (Di and Cameron, Nutrient Cycling in Agroecosystems 46:237-256, 2002) (Erisman et al., Environmental Pollution, 150:140, 149, 2007). However, biological nitrogen fixation (“BNF”) has a significant effect on improving yield of sugar beet, which lowers the cost of beet production and increases its chance of being efficient biofuel feedstock in temperate regions.
Therefore, it would be highly desirable to obtain a composition allowing improved production of plants with reduced use of nitrogen fertilizer.                Some limited attempts to infect novel plant host species with endophytic diazotrophs have been made. No evidence of commercially adequate N2 fixation or growth stimulations by these bacteria within the new hosts is was obtained.        
There are reports of positive yield responses of sugar beet inoculation with N2-fixing strains of Bacillus (Sahin et al. 2004, Plant Soil 265:123; Cakmakci et al. 2006, Biol Biochem 38:1482). However, there remains a need for better strains of N2-fixing bacteria that can colonize sugar beet and reduce fertilizer requirements.